Field of the Invention
The present invention relates to an exhaust gas purification apparatus and method for controlling the same. More particularly, the present invention relates to an exhaust gas purification apparatus and method for controlling the same which controls a catalyst heating period differently to improve performance of a three-way catalyst.
Description of Related Art
Recently, according to an increased usage of vehicles and increased traffic volume, air pollution due to exhaust gas comes to the fore as a serious social problem.
Therefore, governments of every country have set an emission standard of pollutant in exhaust gas such as carbon monoxide (CO), hydrocarbon (HC), nitrogen oxide (NOx) and the like to regulate exhaust gas. Regulations on exhaust gases are becoming more and more strict.
Further, manufacturers of vehicles make a great effort to effectively cope with the strict regulations on exhaust gas. A novel vehicle is manufactured in accordance with an exhaust gas emission standard.
Particularly, to satisfy an exhaust gas emission standard, a three-way catalyst converter in which a noble metal is immersed is mounted in an exhaust system of the vehicle to accelerate the oxidation of hydrocarbon, oxidation of carbon monoxide, and reduction of nitrogen oxide.
The three-way catalyst refers to a catalyst which simultaneously reacts with a hydrocarbon based compound, carbon monoxide, and nitrogen oxide (NOx) which are harmful components of the exhaust gas and remove these compounds. A Pt/Rh, Pd/Rh or Pt/Pd/Rh catalyst is mainly used.
Further, the three-way catalyst performs a function of reducing carbon monoxide and hydrocarbon or reducing nitrogen oxide in response to a change of a lean (excessive oxygen) state and a rich (excessive fuel) state with respect to an air to fuel ratio of exhaust gas.
However, the catalyst performance deteriorates as the three-way catalyst is degrades. However, control of the three-way catalyst is not performed according to a variation in catalyst performance; a catalyst in an exhaust past the warranty period is controlled in the same manner as a new article. Further, when the three-way catalyst is controlled in a region wherein the amount of oxygen storage capacity (OSC) is constant, controlling the three-way catalyst becomes difficult since the catalyst performance variation is large according to the variation of the OSC, and thus catalyst performance deteriorates which generates an increase in emissions, etc.
The information disclosed in this Background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.